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Topological entropy of switched systems
Yu Huang,Xingfu Zhong 대한수학회 2018 대한수학회지 Vol.55 No.5
For a switched system with constraint on switching sequences, which is also called a subshift action, on a metric space not necessarily compact, two kinds of topological entropies, average topological entropy and maximal topological entropy, are introduced. Then we give some properties of those topological entropies and estimate the bounds of them for some special systems, such as subshift actions generated by finite smooth maps on $p$-dimensional Riemannian manifold and by a family of surjective endomorphisms on a compact metrizable group. In particular, for linear switched systems on $\mathbb R^p$, we obtain a better upper bound, by joint spectral radius, which is sharper than that by Wang et al. in \cite{Wang-Ma2015, Wang-Ma-Lin2016}.
Effect of fangchinoline on root resorption during rat orthodontic tooth movement
Xingfu Bao,Min Hu,Yi Zhang,Ferdinand Machibya,Ying Zhang,Huan Jiang,Dongsheng Yu 대한치과교정학회 2012 대한치과교정학회지 Vol.42 No.3
Objective: To evaluate the short-term effect of fangchinoline, an antiinflammatory drug widely used in Asia, on root resorption that is associated with orthodontic tooth movement. Methods: Twenty-four Wistar rats were randomly divided into 6 groups. Mesial forces of 0, 50, or 100 g were applied to the maxillary first molar of the rats in each group for 14 days by activating nickel-titanium closed-coil springs. One-half of the rats receiving each of these treatments also received injections of 200 μL fangchinoline every 2 days. Finally, movement of the maxillary first molars was measured using digitized radiographs. The molars were extracted and the surfaces of the root resorption craters were recorded using a scanning electron microscope. The distance the molars moved and resorptionarea ratio was measured, and results were analyzed using 2-way ANOVA tests. Results: There were no statistical differences in the distances the first molars moved under 50 or 100 g force, regardless of treatment with fangchinoline. However, the resorption area ratios were significantly smaller in those rats that were treated with both tension and fangchinoline than in those rats treated by tension alone. Conclusions: Fangchinoline reduced the resorption area ratio in rats and is therefore an important means of alleviating root resorption.
Effect of fangchinoline on root resorption during rat orthodontic tooth movement
Bao, Xingfu,Hu, Min,Zhang, Yi,Machibya, Ferdinand,Zhang, Ying,Jiang, Huan,Yu, Dongsheng The Korean Association Of Orthodontists 2012 대한치과교정학회지 Vol.42 No.3
Objective: To evaluate the short-term effect of fangchinoline, an anti-inflammatory drug widely used in Asia, on root resorption that is associated with orthodontic tooth movement. Methods: Twenty-four Wistar rats were randomly divided into 6 groups. Mesial forces of 0, 50, or 100 g were applied to the maxillary first molar of the rats in each group for 14 days by activating nickel-titanium closed-coil springs. One-half of the rats receiving each of these treatments also received injections of 200 ${\mu}L$ fangchinoline every 2 days. Finally, movement of the maxillary first molars was measured using digitized radiographs. The molars were extracted and the surfaces of the root resorption craters were recorded using a scanning electron microscope. The distance the molars moved and resorption-area ratio was measured, and results were analyzed using 2-way ANOVA tests. Results: There were no statistical differences in the distances the first molars moved under 50 or 100 g force, regardless of treatment with fangchinoline. However, the resorption area ratios were significantly smaller in those rats that were treated with both tension and fangchinoline than in those rats treated by tension alone. Conclusions: Fangchinoline reduced the resorption area ratio in rats and is therefore an important means of alleviating root resorption.
TOPOLOGICAL ENTROPY OF SWITCHED SYSTEMS
Huang, Yu,Zhong, Xingfu Korean Mathematical Society 2018 대한수학회지 Vol.55 No.5
For a switched system with constraint on switching sequences, which is also called a subshift action, on a metric space not necessarily compact, two kinds of topological entropies, average topological entropy and maximal topological entropy, are introduced. Then we give some properties of those topological entropies and estimate the bounds of them for some special systems, such as subshift actions generated by finite smooth maps on p-dimensional Riemannian manifold and by a family of surjective endomorphisms on a compact metrizable group. In particular, for linear switched systems on ${\mathbb{R}}^p$, we obtain a better upper bound, by joint spectral radius, which is sharper than that by Wang et al. in [42,43].
Effect of Short-Time Carburizing Treatment on Microstructure and Mechanical Properties of M50 Steel
Yinghua Wei,Xingfu Yu,Shuai Wang,Xiangyang Shen,Wenzeng Zhao,Yong Su,Yu Yang,Xiaochuan Feng 대한금속·재료학회 2023 METALS AND MATERIALS International Vol.29 No.6
By using scanning electron microscope (SEM), transmission electron microscope (TEM), X-Ray diffraction (XRD), and hardnessand rotational bending fatigue tests, the effect of short-time carburizing treatment on the microstructure and mechanicalproperties of bearing steel was studied. The results show that when the M50 steel is not carburized, the hardness is 750 HV,the rotational bending fatigue limit is 1100 MPa, and the impact absorption energy is 15.46 J. After short-time carburizationwith the carbon potential of 0.6%, the maximum hardness in the carburized area, the rotational bending fatigue limitand the impact absorption energy are all increased to be 807.7 HV, 1210 MPa and 16.72 J respectively. When the carbonpotential is further enhanced to be 0.8%, the maximum hardness of the carburized area of the steel is further enhanced to be813.4 HV, but the rotational bending fatigue strength and the impact absorption energy are both decreased to be 1125 MPaand 13.65 J respectively, which has close relations with the increasement of undissolved carbides and the precipitation ofacicular carbides.
Research on Nonlinear Vibration Characteristics of Spiral Bevel Gear
Nie Junfeng,Yu Guangbin,Song Ye,Qu Zhigang,Zheng Minli,Zhao Xingfu 보안공학연구지원센터 2016 International Journal of Multimedia and Ubiquitous Vol.11 No.2
Based on the concentrated parameters theory, a 7-freedom coupled vibration dynamic model of the spiral bevel gear transmission system is established, which includes transmission error, time-varying mesh stiffness and the tooth backlash clearance. In the model, the axial vibration, the torsion oscillation of the gear pair aroused by tooth meshing force and the lateral oscillations resulting from flexional deformation of the gear shaft are taken into account. The mesh stiffness fluctuation is developed as 5-order Fourier series and the tooth backlash clearance is fitted by 7-order polynomial function. Through the Gear method, the dynamic response of the system is obtained, and the vibration characteristics are analyzed.
Dynamic Characteristic Simulation of Helicopter Tail Drive Shaft System
Nie Junfeng,Yu Guangbin,Song Ye,Qu Zhigang,Zheng Minli,Zhao Xingfu 보안공학연구지원센터 2016 International Journal of Smart Home Vol.10 No.6
Helicopter with the advantage of light, flexible and hovering in the air, is widely used. In both military and civilian domain, it gets more and more attention. It becomes the main subject of research in the world. In the power transmission system of helicopter, the tail rotor shaft is an important part. It is one of the key technologies to predict the dynamic characteristics of the shaft accurately for improving the overall performance of the helicopter. Based on the theory of elastic mechanics, rotor dynamics and the finite element analysis, the former main drive shaft is taken as an example. The dynamic characteristics of the transmission shaft is calculated by the multi/few degrees of freedom finite element method. The validity of the finite element method with few degrees of freedom is determined. Then the structure characteristics of the helicopter tail drive shaft are analyzed, and the dynamic characteristics of the helicopter tail rotor shaft are calculated by using the finite element method with few degrees of freedom. The research results provide the basis and guidance for the design of the helicopter tail drive system.
Yanxia Xu,Bo Tang,Xingfu Song,Ze Sun,Jianguo Yu 한국화학공학회 2018 Korean Journal of Chemical Engineering Vol.35 No.12
We evaluated the effect of particle size and associated dynamics on a hydrocyclone separation process in order to understand the movement of the particle trajectories inside the hydrocyclone via numerical analysis, with particles of acid hydrolysis residues discharged in TiO2 production via the sulfate method as a case study. The values obtained from the numerical simulation were successfully compared with those from experimental tests in the literature, allowing a description of the dynamics of the particles, their acting forces, and their relevant properties together with separation efficiency. The results showed that particle motion is jointly controlled by the drag force, the pressure gradient force and the centrifugal force. With increasing particle size, the influence of the drag force is weakened, whereas that of the centrifugal force and pressure gradient is strengthened. Factors including particle density, slurry viscosity, and inlet slurry flow rate also contribute to a clear and useful understanding of particle motion behavior in the hydrocyclone as a method for improving the separation efficiency.